1. Field
The present disclosure relates to flow passage devices such as microchannels, which are usable for applications where chemical reactions are a main mechanism for analyses, and relates to a method of producing the flow passage devices. For example, the present disclosure relates to a technology relating to the flow passage device such as a medical microchannel used in genetic tests, protein tests, and so forth.
2. Description of the Related Art
In existing sample tests, fluid reagents are required for chemical analyses, preparation of reagents, chemical syntheses, and reaction detection on the order of milliliters (ml) to microliters (μl). Tests performed using test-tubes or the like can now be performed on the order of nanoliters (nl) by formation of a fine reaction field using a litho-process and a thick film process techniques. The micro total analysis system (μ-TAS) is a technology used for medical tests and diagnoses performed by utilizing such fine reaction fields. That is, the μ-TAS technology is applicable to fields of genetic testing, chromosomal testing, cell testing and so forth, biotechnologies, tests of substances present in very small amounts in the environment, research on the cultivating environment for agricultural products and the like, genetic tests of agricultural products, and so forth.
Existing tests are mainly performed by laboratory technicians who have skills for handling reagents. However, the test processes are complex, and a certain skill levels are required to operate the equipment. In such a technical situation, introduction of the μ-TAS technology has been attracting attention as a significantly advantageous method. The advantages include automatization, increased speed, increased accuracy, cost reduction, promptness, decreased negative effects on the environment, and so forth. Microchannels (flow passages) used for such a μ-TAS technology have fine grooves and holes for introducing the reagents into the grooves. In order to achieve effective reactions of a reagent with a small amount of a sample, a small amount of the reagent needs to be handled without problem. Regarding such a technology, a microchannel has been proposed. With this microchannel, introduction of air bubbles into a flow passage, through which a small amount of a liquid flows, can be avoided (see Japanese Patent Laid-Open No. 2012-168115).
More particularly, as the advanced medical testing systems as described above are generally used, microchannels utilized in the medical testing systems need to be produced. Typical microchannels have flow passages (grooves) as closed spaces and holes for introduction of the reagents into the flow passages. Although the microchannels having fine structures have fine flow passages and holes for handling of the reagents in the structures, the amounts of the reagents are in a different order from the amounts of the reagents used in the existing testing. Thus, there are some difficulties in the production of such flow passages. One of the difficulties is as follows: when a hole formed in a component is connected to a hole formed in another component, the reagent is transferred through the connected holes. However, joining the holes having a fine opening is not an easy task. For example, assuming that the reagent is transferred through holes having about 1-mm openings connected to each other. In this case, when positioning is not accurately performed, the centers of the holes are misaligned with each other. This may lead to formation of a step or a small space due to incomplete engagement of the peripheral portions. This step or small space may cause the opening area of the flow passage to vary, disturb the flow of the reagent in the flow passage, or cause contamination while changing the reagent. In order to address the difficulties, the following structure has been attempted: the diameters of the fine openings are designed to be slightly different from each other and the steps and the small spaces designed in advance are maintained. However, even with this structure, it is not easy to connect the holes with the alignment of the holes completely maintained.